A particular application for a one-part moisture curable, pourable sealer composition that achieves fast, deep curing is in the field of sealing mechanical penetrations in a waterproof membrane covering a roof substrate. In a typical low slope membrane roof, provision must be made for sealing penetrations of the roof by vent pipes, support straps, conduits, guy anchors and similar elements. Generally, a pitch pocket or pan which surrounds the penetrating element is used. Although the invention is useful with generally any type of pitch pocket, examples of preferred pitch pockets are described in commonly owned U.S. Pat. Nos. 5,493,827, and 5,768,838. A sealant is poured into the pitch pocket or pan around the penetrating element. Generally a two-part urethane pourable sealant composition is used. An advantage with two-part pourable urethane sealant compositions is that they set in approximately two hours to form a solid composite seal with the perimeter or inner surface of the walls or curbs of the pitch pocket. However, a disadvantage with the two-part pourable urethane sealant compositions is that they must be shipped to the site at which they are used in two separate parts that are mixed just prior to being poured into a pitch pocket. Thus, the use of a two-part pourable urethane sealer composition, as opposed to a one-part sealer composition, involves an additional undesirable step. Additionally, care must be taken during the mixing step to insure that the two components are thoroughly mixed, and mixed in the proper proportions, as improper mixing can adversely affect performance of the roof penetration seal. Thus, a one-part sealant composition that eliminates the need for mixing would be highly desirable.
One-part sealants have been used for sealing mechanical penetrations in a waterproof membrane covering a roof substrate. However, the one-part sealants that have been used heretofore have disadvantages. For example, molten asphalt or coal tar have been used as one-part sealants for sealing roof penetrations. These materials shrink upon curing, and exhibit poor weatherability. Also, because of their thermoplastic nature, they often melt and run into a building. This can lead to disastrous results in a fire situation. Solvent-based asphalt and rubber-modified asphalt have also been used as one-part sealants for sealing roof penetrations in a waterproof membrane covering a roof substrate. However, these products have generally all of the same disadvantage associated with bituminous materials (e.g., molten asphalt or coal tar), and exhibit even greater shrinkage caused by evaporation of the solvent. One-part moisture curable urethanes have also been used. Although one-part moisture curable urethanes are thermosetting, known one-part urethane sealants are capable of only shallow cures, usually less than ⅜ inch deep. Deeper cures of at least 2 inches are desired. Inadequate depth of cure can result in splitting and cracking of the seal. Cure times for these one-part moisture curable urethanes have been extremely lengthy. Also, they contain small amounts of solvent that can cause volume shrinkage when poured into a pitchpan.
Accordingly, there remains a need for a one-part pourable sealant that is thermosetting, non-shrinking, and capable of quickly curing in a closed cavity to a depth of at least two inches.